Disclaimer: Elixir is extremely productive, Phoenix is outstanding, the community is world-class, and as a result of the Erlang VM / OTP / Beam you can remove whole parts of your traditional webstack. If you haven't tried it I cannot recommend it enough.
But!
As a long-time Elixir Developer who has gladly used it to bootstrap many applications and companies, I have to say I think this article is actively harmful to the community.
It's an extremely thinly veiled sales pitch for their "Petal Pro" paid boilerplate.
At the same time, it does nothing to address the tradeoffs of certain features like Live View. Which for the record is a poor fit if your app suffers from client-side latency or requires any kind of offline-enabled features.